In recent years, electronic apparatuses have been increasing in variety and the number of functions provided therefor has been increasing, so that many kinds of electronic apparatuses are provided with display panels to improve the operability. As the display panels, for example, ones comprising liquid crystal are used. The display panels are structured so as to display operation menu information, the information entered by the user and the like. Display panels of this kind can be used as effective advertising media.
For example, Japanese Laid-open Patent Application No. H5-264954 describes an advertisement information display element using a ferroelectric polymeric liquid crystal having memory capability. Japanese Laid-open Patent Application No. H5-264949 describes a menu apparatus using a ferroelectric polymeric liquid crystal. On this apparatus, letters can be directly written by use of a touch panel.
Japanese Laid-open Patent Application No. H10-21457 discloses a vending machine where product information and advertisement information are displayed on a display panel using a ferroelectric liquid crystal.
However, in displays of the above-described kind, the following are unsolved: to display an operation display function of the apparatus and an advertisement display function without deteriorating the ease of use of the apparatus while achieving energy conservation; and to efficiently update the advertisement display. Thus, an advertising method desirable for the users of the apparatuses, distributors, advertising agents, information service firms and the like is yet unrealized.
Also, when a new electronic apparatus is placed on the market, the usage charge (i.e., fee) of the apparatus is generally set to be high, which hinders wider use of the apparatus. For this reason, a charging method and a charging system with which apparatuses more easily spread is required.
It is also noted that, at present, there are approximately 40 million portable telephone subscribers in Japan; however, problems arise such that the cost to the users is high, that portable telephones are not made use of except when telephone calls are made and that portable telephone apparatuses look similar and it is therefore difficult to distinguish one's telephone apparatus from others'.
In recent years, various kinds of reflective liquid crystal display devices in which liquid crystal exhibiting the cholesteric phase such as cholesteric liquid crystal or chiral nematic liquid crystal is sandwiched between two substrates have been researched and developed. This type of liquid crystal having the cholesteric phase has several advantages even though the writing time is slightly slower than those of TN liquid crystal, STN liquid crystal and the like typically used as display means. Specifically, in the cholesteric liquid crystal display, after information is displayed, the display is maintained even after voltage application is stopped (memory capability is provided), and since the liquid crystal is reflective, no backlight is necessary and bright and high-resolution full-color display can be easily provided. Therefore, it is expected that various novel and useful additional values can be created by providing such a reflective liquid crystal display device having memory capability on a battery-operated portable communication terminal. Such a reflective liquid crystal display device having memory capability is suitable for use as secondary display means of a battery-operated portable communication terminal.
However, liquid crystal exhibiting the cholesteric phase has a problem that the driving voltage is comparatively high. On the other hand, in order that the portability is not impaired, portable communication terminals are required to be capable of maintaining a communicating state and a standby state for a long time with the limited power of the battery. Thus far, a high-power battery that meets this requirement cannot be used even though the above-described type of liquid crystal display device is provided.
Further, when the liquid crystal display device having memory capability and a communication circuit that requires particularly high power among the parts of the portable communication terminal are driven at the same time, the peak current increases to raise a possibility that communication is interrupted. This problem is particularly likely when the battery becomes weak.